Generally, a radio access network (“RAN”) is comprised of the radio network controller (“RNC”) and the node B, where the RNC is connected to the core network (“CN”), which is a switching network through the Iu interface, and the node B is connected to the user equipment (“UE”) through the radio interface.
The protocol architecture of the radio interface is comprised of layer 1 (physical layer), layer 2 (data link layer) and layer 3 (network layer), where a logical channel is defined between layer 3 and layer 2 and a transport channel is defined between layer 2 and layer 1.
Layer 2 is divided into two sub-layers, namely the radio link control (“RLC”) for controlling a radio link and medium access control (“MAC”) for controlling radio resource assignment and so on.
Furthermore, layer 3 is divided into the C-plain for implementing call setting control and the U-plain for implementing user information transmission. The C-plain is further divided into the radio resource control (“RRC”) for directly controlling layer 1 and layer 2 and the non-access stratum (“NAS”) for implementing higher-layer control. Here, mobility management (“MM”) is a function that plays a central role in the NAS.
RRC provides several services, including reporting of broadcast information to all UEs in the area, calling out a specific UE, and setting, changing and releasing connections, and plays an important role in call connection between the UE and the network.
For establishing a call between the UE and the network, it is necessary to transmit messages including a great amount of information as setting information (hereinafter information element or “IE”), which is a factor of delay in call connection. Messages having particularly a large amount of information include an RRC connection setup message (for establishment of control information channel) and a radio bearer setup message (for establishment of traffic data channel) for establishing a radio channel.
Here, the method of reducing a call connection delay, called “preconfiguration,” (generic term for default configuration, predefined configuration and stored configuration) for reducing the size of a message related to call connection is standardized in the 3rd generation partnership project (“3GPP”). Preconfiguration will be explained below.
As for preconfiguration, Non-Patent Document 1 defines two methods based on the basic concept of holding representative information in the UE and reporting only indexes from the network to the UE without transmitting radio channel establishment information as needed.
First, the default configuration will be explained. In the default configuration, configuration patterns are set up by assigning indexes (14 types) to configuration patterns defined in advance (see section 2 of Non-Patent Document 1 for details), making the UE hold these indexes and reporting the indexes from the network.
Thus, the indexes are the only information (messages such as the RRC connection setup message and radio bearer setup message) that is transmitted from the network, and so the size of these messages can be reduced significantly, so that it is possible to reduce call connection delay. By the way, only the configuration patterns that are defined can be used, and so it is not possible to perform operator-specific setting or UE-specific setting.
Next, the predefined configuration will be explained. In the predefined configuration, configuration patterns and the corresponding indexes (16 types) are transmitted using a channel broadcasted from the network. The UE receives broadcast information transmitted from the network in an idle state or the like and holds the configuration patterns and indexes. The UE reports whether or not the UE has the relationships between the configurations and indexes to the network upon transmitting an RRC connection request message.
On the other hand, when it is decided that the UE holds the broadcast information, the network can transmit indexes alone as in the default configuration and reduce the size of messages, so that it is possible to reduce call connection delay. Unlike the default configuration, the predefined configuration enables operator-specific setting. However, radio resources are used wastefully taking into account the UE not using the configuration transmitted in broadcast information.
Here, FIG. 1 shows a multi-call channel structure. As shown in FIG. 1, three signaling radio bearers (“SRBs”) are provided for control signals, and a transport channel is assigned to each SRB. Furthermore, multi-call including packet call and speech call is assumed here, and so radio access bearer (“RAB”) 20 and RAB5 are provided as traffic data (the RAB numbers are examples). Transport channels are assigned to these RAB's. Therefore, in the example of FIG. 1, five transport channels are mapped to the physical channel.
As a message for making the setting shown in FIG. 1 in the UE, FIG. 2 shows an RRC connection setup message as an example, and FIG. 3 shows a radio bearer setup message as an example. As shown in FIG. 2 and FIG. 3, the preconfiguration applies only to the RB setting IE and the TrCH setting IE. Here, as shown in FIG. 4, the predefined configuration is applied such that the details set up by the predefined configuration are common in the operator. That is, the setting details need to be the same across cells.    Non-Patent Document 1: 3GPP TR25.331, “Radio Resource Control (RRC) Protocol Specification”    Non-Patent Document 2: Signaling Enhancements for CS and PS Connection Analyses and Recommendations